Locations not served by municipal sewage systems and the like must utilize residential or commercial wastewater treatment systems to treat wastewater. Residential and commercial wastewater typically includes all kinds of particles and organisms, including bacteria such as e coli and viruses. As a result, at some locations, wastewater treatment must be followed by ultraviolet germicidal irradiation (UVGI). Ultraviolet germicidal irradiation (UVGI) is a disinfection method that utilizes ultraviolet (UV) light, particularly short-wavelength ultraviolet (UV-C) light, to kill and/or inactivate microorganisms by destroying nucleic acids and disrupting their DNA, leaving them unable to perform vital cellular functions.
UV light or energy is found in the electromagnetic spectrum between visible light and x-rays. In order to kill microorganisms, the UV light rays must strike the cells. Upon striking a cell, the UV energy penetrates the outer cell membrane, passes through the cell body and disrupts its DNA to prevent reproduction. Thus, the water is not altered chemically because nothing is added except for the UV energy. However, the sterilized microorganisms are not removed from the water and UV light disinfection does not remove dissolved organic or particles in the water. Thus, UV light disinfection should be used in conjunction with wastewater treatment means for biochemical oxygen demand (BOD) and total suspended solids (TSS) removal and reduction. As a result, wastewater treatment systems often include a primary treatment removing solids, fats, oils, greases etc., a secondary treatment degrading impurities such as anaerobic and/or aerobic filtration, and a tertiary treatment of disinfection such as by UV light.
The degree of inactivation by ultraviolet energy is directly related to the dose of UV applied to the water. The dosage, a product of UV light intensity and exposure time, is typically measured in microwatt second per square centimeter (uws/cm2). Most UV disinfecting devices are designed to provide a dosage greater than 30,000 uWS/CM2 after one year of continuous operation. Typically, UV disinfection devices for wastewater treatment systems utilize lamps that produce ultraviolet radiation at about 254 nm, which is the optimal wavelength for disinfection and ozone destruction. However, some ultrapure water treatment systems use ultraviolet radiation 185 nm for reducing total organic carbon (TOC).
While there are ultraviolet light disinfection products for wastewater treatment systems currently available on the market, these products may not be as durable, serviceable, and/or effective as desired. These current products are particularly not very effective flow rate is relatively high such as in some pumped wastewater treatment systems. Accordingly, there is a need in the art for improved ultraviolet light disinfection devices for wastewater treatment systems.